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William Entriken

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This article is cross-posted at https://0xcert.org/news/live-testing-smart-contracts-with-estimategas-william-entriken-tadej-vengust.

Testing smart contracts live without spending gas

0xcert is publishing a series of tech papers in collaboration with various authors. The present article is a contribution by our advisor and the lead author of ERC-721 standard, William Entriken, and our lead blockchain engineer, Tadej Vengust. Live Testing Smart Contracts with ESTIMATEGASWritten by: William Entriken, Tadej Vengust
In this article, we will introduce a technique that allows you to test any deployed contract in arbitrary ways, without spending gas. It works on Ethereum Mainnet, Wanchain, Ethereum Ropsten, Hyperledger Burrow, Proof of Authority Network, private chains, and every other network based on Ethereum Virtual Machine. This new technique was first shown with the ERC-721 Validator, and you can't do it with Truffle.
You will want to learn this technique if:
Your contract deployment …

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A hash tree, or a Merkle tree, is a data structure that allows you to take a lot of information and summarize it together in such a way that you (the "prover") can succinctly prove to somebody else (the "skeptic") that certain data is included.
Background
Here is a typical Merkle-tree implementation:

Arrows represent inclusion in a hash. For example, A = hash(B, C). Hash() is customarily sha256().

Facts F1, F2, F3 and F4 are private. Or, a lighter requirement, there are just so many facts that you cannot be bothered to explain them to somebody else. You will publish root node A, the hash root. And this is proof to the world that this entire tree is encoded in A (if you choose to expose the tree). This rests on the worldwide assumption that hashes don't collide. If somebody is interested to confirm that F3 is included in A then you must share with them F4 and B so that they can recalculate A and confirm it matches the A you published.

This article briefly reviews the Algorand technical paper as well as their white paper for investors. I don't know if the investor paper is public, so I wont link to it. But if you have seen you then you will know you have the right on if:

Technical analysis:
You can see the weaknesses in these strong assumptions in the white paper.

• "[Adversaries] cannot interfere in any way with the messages exchanges among honest users.
We assume that every propagated message reaches almost all honest users in a timely fashion."
* "each small set of players associated to a step ... most probably has empty intersection with the…

Read time: 6 minutes. This post explains how ERC-721 works and does not require any prior knowledge of Ethereum or blockchain.简体中文 --> http://www.sfgroup.hk/news_post/通俗易懂的告诉你什么是erc-721/ （奇点财经翻译）
How does your phone connect to a web server?
Most of your time on computers/phones/technology is spent with a web browser accessing a web page. Most of the screens you see out in the world that display information are usually using a web page to show it, but they just hide the URL bar.

The flight arrivals screen -- it's just a web page
Think for a minute about how this ubiquitous technology works.

You. You are very busy and you are trying to access some information, maybe cat videos or sports scores or your family members' feedback on a photo you posted of your kid. Your phone, or whatever other device is in your hand, that acts on your behalf.The web server decides how it wants to reply to your request.
Technology people, the ones that make your phone and the web servers, refer to y…

Right now Web 3.0, "the blockchain", the decentralized web, etc. are making a lot of people rich. People will do anything to get a few Ether so they can spend it on a pictures of kitties or whatever. Here is the current best practice of how you can get Ether:

Send Western Union payment to somebody recommended by a company that is not in your legal jurisdiction to get Bitcoin, then using an exchange also not in your jurisdictionCreate an account in the United States which requires your social security number, your bank account website usernames/passwords (not a typo), and uncontrolled access to your computer's webcam
In other words, this is shady AF.

At one end of the respecting-regulation spectrum is Uber which says "we're not a taxi and we refuse to follow any taxi laws." But the Web 3.0 players are on the other end where they collect more information from you than any traditional bank.